Thinking of developing a simple Unity game, any ideas?

I would like to learn some more things in unity and test out my skills. I need some ideas for a simple, small Unity game.
Keep in mind that...

1. I still don't know how to do a lot of things, such as making efficient code, or anything like that.
2. I'm just one person. Don't expect it to be a high-quality game.
3. It should be single-player. This is just a way for me to learn more Unity stuff, not create a MOBA or whatever.
4. Keep it simple. I'm no Unity expert. I just want to learn.
5. Don't let your expectations go too high.
6. If possible, there should be a working example of what the game should look like (like an existing game)
7. If it turns out good, I might actually publish it. And you'll get credit for some of it :)

Other than that, you can basically suggest anything. A game about bananas and spaceships, a 2D platformer, a simple mobile game, you name it.
Looking forward to see what you guys come up with! :D